Audiometer attenuator

ABSTRACT

In the audiometer attenuator disclosed herein, an attenuating resistance array and a pair of taps co-operating with the array are arranged so that both the taps and the array are movable. In this way a variety of relative attenuation adjustments may be provided between a signal source and two transducers attenuators having different frequency response characteristics. In particular, movement of the resistance array itself provides for frequency compensation for one of the transducers while movement of one of the taps provides for frequency compensation for the other transducer. Movement of the other tap provides an independent attenuation adjustment which is indicative of hearing loss independently of which transducer is employed.

ilaited States Patent Arguimhau et al.

[ 1 Aprthwm 1 AUDEOMETER ATTENUATOR Grason-Stadley Company, Inc., West Concord, Mass.

[22] Filed: Mar. 24, 1970 [21] Appl.No.: 22,359

[73] Assignee:

FOREIGN PATENTS OR APPLICATIONS 648,653 1/1951 Great Britain ..l79/l N Primary Examiner-Kathleen H. Clafi'y Assistant ExaminerI-lorst F. Braunder Attorney-Kenway, Jenney & Hildreth 57 ABSTRACT In the audiometer attenuator disclosed herein, an attenuating resistance array and a pair of taps co-operating with the array [52] U.S. Cl. ..179/1 N are arranged so that both the taps and the array are movable. [51] Int. Cl ..lH04r 29/00 In this way a variety of relative attenuation adjustments may [58] Field of Search ..179/l N, 1 AA, lMN be provided between a signal source and two transducers attenuators having different frequency response characteristics. [56] References Cited In particular, movement of the resistance array itself provides for frequency compensation for one of the transducers while NI STATES PATENTS movement of one of the taps provides for frequency compen 3,222,456 12/1965 Hyman ..179/1 N 5:: 2,985,718 5/1961 I-Iunsicker et al ..179/l N dicative of hearing loss independently of which transducer is employed.

9 Claims, ll Drawing Figure OSCILLATOR 2] -23 33 39 x I f' T 27 PATENTED-APR 4 I972 moEjQwo ATTORNEYS AUDIOMETER ATTENUATOR BACKGROUND OF THE INVENTION This invention relates to an audiometer attenuator and more particularly to such an attenuator which is adapted for use with two transducers having different frequency response characteristics.

In various prior art audiometers known heretofor, attenuators have been provided with two means of adjustment, one coupled to the signal source, e.g., by means of a cam, so as to provide frequency compensation and a second which provides a measure of hearing loss or acuity. The frequency compensation provided, however, was typically correct only for one transducer, or at the most one type of transducer. In changing from one type of transducer to another, e.g., from an air conduction headphone to a bone vibrator transducer, it was typically necessary to modify the frequency compensation function, e.g., by substituting one cam for another.

Among the several objects of the present invention may be noted the provision of an audiometer attenuator which automatically provides compensation for two different types of transducers; the provision of such an attenuator which permits one adjustment means to be calibrated directly in hearing loss and to be accurate for either of the two transducers employed; the provision of such an attenuator in which the compensation characteristic for each transducer may be independently determined; the provision of such an attenuator which is reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.

SUMMARY OF THE INVENTION Briefly, an attenuator according to the present invention is adapted for use in an audiometer employing two different types of transducer. The attenuator comprises an attenuating resistance array and a pair of movable taps which co-operate with the array. One of the transducers is connected to a fixed point on the array while the other transducer is connected to one of the taps. A test tone signal source is connected to the other of the taps. Accordingly, by varying the position of the array, the attenuation between the source and the first transducer may be varied, while movement of the first tap will vary the attenuation between the second transducer and the source. Movement of the second tap varies the attenuation between the source and both transducers and thus the drive means for this tap may be calibrated directly in terms of hearing loss or acuity.

BRIEF DESCRIPTION OF THE DRAWING The single drawing is a somewhat diagrammatic illustration of audiometric apparatus employing an attenuator according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is indicated at 11 a variable frequency oscillator suitable for audiometric use. Oscillator 1 1 is adapted to drive, through the attenuator apparatus indicated generally at 13, either an air conduction headphone or a bone conduction transducer, i.e., a bone vibrator as indicated at 17. The oscillator output frequency is controllable by means of a calibrated knob 18.

The attenuating apparatus 13 comprises a resistance network or array, indicated at 19 generally, mounted on an elongate support member 20. As illustrated, the resistance array 19 comprises a conventional ladder array of resistances cooperating with a common ground 22. As is understood by those skilled in the art, this array has the characteristic that the attenuation, expressed in decibels, between two points along the array is substantially proportional to the separation between the two points.

A pair of movable taps for making connections to selected points along the array are indicated at 21 and 23. Both the taps 21 and 23 and the resistance array support member 21 are assumed to be slidable laterally, e.g., by means of suitable guides (not shown). The air conduction headphones 15 are connected to the right-hand end of the attenuating resistance array, while the bone vibrator 17 is connected to the movable tap 23. The output signal from the oscillator 11 is applied to the array through the movable tap 21. Suitable flexible leads are provided, as indicated in the drawing by coils, to permit relative movement of the resistance array and the taps.

In addition to controlling the output frequency of the oscillator 11, the knob 18 also simultaneously operates a pair of cams 27 and 29. Operating through suitable cam followers 31 and 33, the cams 27 and 29 drive or determine the lateral positions of the resistance array support member 20 and the movable tap 23 respectively. As is described in greater detail hereinafter, the shapes of the cams 27 and 29 are generated as special functions to compensate for the frequency response characteristics of the air conduction ear phones 15 and the bone vibrator 17, respectively. As is usual in audiometer applications, the compensation takes into consideration the response of a normal subject to the particular type of transducer as well as the frequency response of the transducer itself.

The lateral position of the movable tap 21 is determined by a rack 37 which is driven by a pinion 39. The pinion 39 is in turn controlled or driven by means of a suitable calibrated knob, as indicated at 41.

The operation of this apparatus when using the air conduction ear phones 15 is substantially as follows. As the knob 18 is operated to vary the output frequency of the oscillator 11, the cam 27 moves the resistance array 19 according to a predetermined function such that the resulting variation in attenuation between the tap 21 and the right-hand end of the resistance array 19 is such as to compensate for the frequency response characteristics of the headphones themselves. In accordance with conventional practice, the subject being tested operates the knob 41 or some other conventional drive mechanism so as to maintain the sound level produced by the headphone substantially at threshold level. The setting of knob 41 thus indicates the subjects response to the signals being reproduced in the headphones. Since the cam 27 is shaped to compensate for both the frequency response of the headphone and for a normal subjects response, the knob 41 may be calibrated directly in terms of acuity or hearing loss. Since the air conduction transducer is connected directly to the array, contact noise is reduced. This is of particular advantage with the air conduction transducer which is typically more sensitive than the bone vibrator.

When using this apparatus with the bone vibrator 17, the effective total attenuation is determined by the separation between the two taps 21 and 23. The cam 29 is shaped to compensate for the frequency response characteristics of the bone vibrator itself together with the response characteristic of a normal subject to this type of transducer. Again, adjustment of the lateral position of the tap 21 by means of the knob 41 allows the sound level produced by the bone vibrator 17 to be maintained at the subject's threshold level. Since the frequency response characteristic compensation is accomplished by means of a separate cam 29, the calibration of the setting of knob 41 will still be in terms of hearing acuity or hearing loss and the same scale may be used for both the air conduction headphone transducer 15 and the bone vibrator transducer 17. While adjustment of the oscillator frequency by means of the knob 18 will also cause the resistance array support member 20 to be laterally displaced by the cam 27, it should be noted that the attenuation provided between the source 11 and the bone vibrator 17 is independent of the shape of the cam 27 since this attenuation depends solely on the spacing between taps 21 and 23. Similarly, the attenuation provided between the source 11 and the air conduction transducer 15 is independent of the shape of the cam 29. Thus, separate and independent compensations can be provided.

While the attenuator of the present invention has been shown in a linear form for simplicity of illustration, it should be understood that this attenuator may be readily fabricated in rotary form in straightforward manner. In such a case, the resistance array 11% is preferably distributed around a conventional potentiometer body, while the taps 21 and 23 are constituted by wipers mounted on co-axial shafts. Likewise, in audiometers employing masking noise for preventing hearing of the test tone in the ear opposite that being tested, a second attenuator according to the invention may be employed in the noise signal path.

In view of the foregoing, it may be seen that several objects of the present invention are achieved and other advantageous results have been attained.

As various changes could be made in the above construction without departing from the scope of the invention, it should be understood that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. in an audiometer, attenuating apparatus for energizing two different transducers, said attenuating apparatus comprising:

a resistance support member;

an attenuator resistance element distributed along a predetermined path on said member;

a first tap movable along said path for establishing a first connection to said array;

means for applying a signal to said first tap for introducing said signal into said array;

means for connecting a fixed point on said array to one of said transducers;

a second tap movable along said path for establishing a second connection to said array; and

means for connecting said second tap to the other of said transducers.

2. Apparatus as set forth in claim 1 wherein said resistance element is a ladder array of resistances.

3. In an audiometer, attenuating apparatus for energizing two different transducers each in accordance with a respective response characteristic, said attenuating apparatus comprising:

a resistance support member;

an attenuator resistance array distributed along a predetermined path on said member;

means for generating a signal of preselectable frequency;

a first tap movable along said path for establishing a first connection to said array;

means for connecting said signal generating means to said first tap for introducing said signal into said array;

means for connecting one end of said array to a first transducer having a first characteristic response with respect to frequency;

a second tap movable along said path for establishing a second connection to said array;

means for connecting said second tap to a second transducer having a second characteristic response with respect to frequency;

a first drive means, said first drive means operating to displace said member in a path paralleling said predetermined path to effect relative motion between said array and said taps, said drive means being coupled to said signal generating means with the displacement proceeding as a first predetermined response compensating function of the frequency of said signal;

a second drive means, said second drive means operating to displace said second tap along said predetermined path to effect relative motion between said second tap and said array, said second drive means being coupled to said signal generating means the displacement proceeding as a second predetermined response compensating function of the frequency of said signak and a third drive means said third drive means operating to displace said first tap along said predetermined path to effect relative movement between said first tap and said array and thereby vary the attenuation between said signal generating means and both of said transducers.

4. Apparatus as set forth in claim 3 wherein said first transducer is an air conduction headphone and said second transducer is a bone vibrator.

5. Apparatus as set forth in claim 4 wherein said third drive means is calibrated as a function of hearing loss with respect to either transducer.

6. Apparatus as set forth in claim 3 wherein said first drive means includes a cam shaped to compensate for the frequency response characteristic of said first transducer.

7. Apparatus as set forth in claim 3 wherein said second drive means includes a cam shaped to compensate for the frequency response characteristic of said second transducer.

8. In an audiometer, attenuating apparatus for energizing two different transducers each in accordance with a respective response characteristic, said attenuating apparatus comprising:

a resistance support member;

a ladder resistance array distributed along a predetermined path on said member;

means for generating a signal of preselectable frequency;

a first tap movable along said path for estabiishing a first connection to said array;

means for connecting said signal generating means to said first tap for introducing said signal into said array;

means for connecting one end of said array to a first trans ducer having a first characteristic response with respect to frequency;

a second tap movable along said path for establishing a second connection to said array;

means for connecting said second tap to a second transducer having a second characteristic response with respect to frequency;

a first drive means including a cam, said first drive means operating to displace said member in a path paralleling said predetermined path to effect relative motion between said array and said taps, said cam being coupled to said signal generating means and being shaped so that the displacement proceeds as a predetermined response compensating function of the frequency of said signal, which function compensates for the frequency response characteristic of said first transducer;

a second drive means including a cam, said second drive means operating to displace said second tap along said predetermined path to effect relative motion between said second tap and said array, the respective cam being coupled to said signal generating means and being shaped so that the displacement of said second tap proceeds as a predetermined response compensating function of the frequency of said signal which compensates for the frequency response characteristic of said second transducer; and

a third drive means, said third drive means operating to displace said first tap along said predetermined path to effect relative movement between said first tap and said array and thereby vary the attenuation between said signal generating means and both of said transducers, said third drive means being calibrated as a function of hearing acuity.

9. Apparatus as set forth in claim 8 wherein first transducer is an air conduction headphone and said second transducer is a bone vibrator. 

1. In an audiometer, attenuating apparatus for energizing two different transducers, said attenuating apparatus comprising: a resistance support member; an attenuator resistance element distributed along a predetermined path on said member; a first tap movable along said path for establishing a first connection to said array; means for applying a signal to said first tap for introducing said signal into said array; means for connecting a fixed point on said array to one of said transducers; a second tap movable along said path for establishing a second connection to said array; and means for connecting said second tap to the other of said transducers.
 2. Apparatus as set forth in claim 1 wherein said resistance element is a ladder array of resistances.
 3. In an audiometer, attenuating apparatus for energizing two different transducers each in accordance with a respective response characteristic, said attenuating apparatus comprising: a resistance support member; an attenuator resistance array distributed along a predetermined path on said member; means for generating a signal of preselectable frequency; a first tap movable along said path for establishing a first connection to said array; means for connecting said signal generating means to said first tap for introducing said signal into said array; means for connecting one end of said array to a first transducer having a first characteristic response with respect to frequency; a second tap movable along said path for establishing a second connection to said array; means for connecting said second tap to a second trAnsducer having a second characteristic response with respect to frequency; a first drive means, said first drive means operating to displace said member in a path paralleling said predetermined path to effect relative motion between said array and said taps, said drive means being coupled to said signal generating means with the displacement proceeding as a first predetermined response compensating function of the frequency of said signal; a second drive means, said second drive means operating to displace said second tap along said predetermined path to effect relative motion between said second tap and said array, said second drive means being coupled to said signal generating means the displacement proceeding as a second predetermined response compensating function of the frequency of said signal; and a third drive means said third drive means operating to displace said first tap along said predetermined path to effect relative movement between said first tap and said array and thereby vary the attenuation between said signal generating means and both of said transducers.
 4. Apparatus as set forth in claim 3 wherein said first transducer is an air conduction headphone and said second transducer is a bone vibrator.
 5. Apparatus as set forth in claim 4 wherein said third drive means is calibrated as a function of hearing loss with respect to either transducer.
 6. Apparatus as set forth in claim 3 wherein said first drive means includes a cam shaped to compensate for the frequency response characteristic of said first transducer.
 7. Apparatus as set forth in claim 3 wherein said second drive means includes a cam shaped to compensate for the frequency response characteristic of said second transducer.
 8. In an audiometer, attenuating apparatus for energizing two different transducers each in accordance with a respective response characteristic, said attenuating apparatus comprising: a resistance support member; a ladder resistance array distributed along a predetermined path on said member; means for generating a signal of preselectable frequency; a first tap movable along said path for establishing a first connection to said array; means for connecting said signal generating means to said first tap for introducing said signal into said array; means for connecting one end of said array to a first transducer having a first characteristic response with respect to frequency; a second tap movable along said path for establishing a second connection to said array; means for connecting said second tap to a second transducer having a second characteristic response with respect to frequency; a first drive means including a cam, said first drive means operating to displace said member in a path paralleling said predetermined path to effect relative motion between said array and said taps, said cam being coupled to said signal generating means and being shaped so that the displacement proceeds as a predetermined response compensating function of the frequency of said signal, which function compensates for the frequency response characteristic of said first transducer; a second drive means including a cam, said second drive means operating to displace said second tap along said predetermined path to effect relative motion between said second tap and said array, the respective cam being coupled to said signal generating means and being shaped so that the displacement of said second tap proceeds as a predetermined response compensating function of the frequency of said signal which compensates for the frequency response characteristic of said second transducer; and a third drive means, said third drive means operating to displace said first tap along said predetermined path to effect relative movement between said first tap and said array and thereby vary the attenuation between said signal generating means and both of said transducers, said third drive means being calibrated as a function of hearing acuIty.
 9. Apparatus as set forth in claim 8 wherein first transducer is an air conduction headphone and said second transducer is a bone vibrator. 